Support multiple rounds of opt_design in Innovus plugin

[jerryz123]

Most designs should only run 1 round.
This is very occasionally useful, and should be used judiciously

Related PRs / Issues

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• Change to core Hammer
• Change to a Hammer plugin
• Other

Contributor Checklist:

• Did you set master as the base branch?
• Did you state the type-of-change/impact?
• Did you delete any extraneous prints/debugging code?
• (If applicable) Did you add documentation for the feature?
• (If applicable) Did you update the poetry.lock file if you updated the requirements in pyproject.toml?
• (If applicable) Did you add a unit test demonstrating the PR?
• (If applicable) Did you run this through the e2e integration tests?
• (If applicable) Did you update the submodules in e2e/ if this feature depends on updated plugins?

[harrisonliew]

Not a fan of this, for a few reasons:

• There appears to be an -incremental flag, although this disables hold & power opts
• Even more targeted: a -targeted flag to only change specific paths
• We should probably change the opt category attributes to tune this behavior. User guide also suggests this between iterations of opt.
• If hold is a concern, we can do an opt_design -post_cts -hold at the end of CTS
• We should also be using opt_signoff after opt_design anyway